12 Pack HW 9 Volt Rechargeable Batteries, USB-C Lithium $32.40 + Free Shipping w/Prime or $35+

stilwebm

Sep 13, 2026 10:45 PM

148 Comments

Joined Aug 2009

stilwebmSep 13, 2026 10:45 PM

148 Comments

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Do not use rechargeable batteries in smoke detectors despite the compatibility claim on the product page. Instead of a slow voltage decline, they drop suddenly, so you may never get a low battery warning, or if you do, it's too late for the alarm to work.

Also it looks like the batteries are the size of a soda can in the AI pic.

2

drl136us

Sep 13, 2026 11:45 PM

459 Comments

Joined Nov 2020

drl136usSep 13, 2026 11:45 PM

459 Comments

Finally rechargeable 9Vs!

chrispitude

Sep 13, 2026 11:50 PM

285 Comments

Joined Jan 2015

chrispitudeSep 13, 2026 11:50 PM

285 Comments

Quote from stilwebm

:

Do not use rechargeable batteries in smoke detectors despite the compatibility claim on the product page. Instead of a slow voltage decline, they drop suddenly, so you may never get a low battery warning, or if you do, it's too late for the alarm to work.

Also it looks like the batteries are the size of a soda can in the AI pic.

They might be okay in dual-supply 120VAC/9VDC detectors.

lottathought

Yesterday 1:43 AM

1.4K Comments

Joined Oct 2006

lottathoughtYesterday 1:43 AM

1.4K Comments

I would be very curious as to how durable and reliable these are. Between pinpointers in metal detecting and door locks, multimeters, ect.... these would get a fair bit of use.

Hotsoup

Yesterday 2:01 AM

493 Comments

Joined Dec 2004

HotsoupYesterday 2:01 AM

493 Comments

I got a 4-pack of the black "version" of the HW 9V's 2 years ago. I have no idea how they are different from these ones.

I use them in the wireless keypad, garage opener and smoke detector. They seems to be working OK. I test the smoke detectors quarterly and swapping them out bi-yearly.

A 12-pack is a lot of 9Vs...

Last edited by Hotsoup September 13, 2026 at 08:11 PM.

1

b-t-1

Yesterday 8:21 AM

1.5K Comments

Joined Nov 2018

b-t-1Yesterday 8:21 AM

1.5K Comments

Quote from chrispitude

:

They might be okay in dual-supply 120VAC/9VDC detectors.

I spring for the money for proven disposables for safety devices, even though I love Eneloops (which these are definitely not).

1

jmhinkle

Yesterday 8:42 AM

1.1K Comments

Joined Mar 2014

jmhinkleYesterday 8:42 AM

1.1K Comments

Quote from stilwebm

:

Do not use rechargeable batteries in smoke detectors despite the compatibility claim on the product page. Instead of a slow voltage decline, they drop suddenly, so you may never get a low battery warning, or if you do, it's too late for the alarm to work.

Also it looks like the batteries are the size of a soda can in the AI pic.

Absolute horseshite. It's not like they go from 9V to 0 in a millisecond. Unless you have some Tim Taylor 40Amp Binford smoke detectors, the drain is super slow. Stop trying to be a fear monger. Been using the Lithium 9V rechargables from another brand for 2 years now. They work great. They perform exactly as a normal 9V does in a smoke detector. They get low, they trip the dreaded chirp that you have to chase through the house to figure out it is the hardest one to reach.

1

12 Pack HW 9 Volt Rechargeable Batteries, USB-C Lithium $32.40 + Free Shipping w/Prime or $35+

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